The invention is concerned with caprolactone-containing vinyl polymers and coating compositions containing the same.
It is known that .epsilon.-caprolactone of the formula: ##STR1## will react with acids or alcohols by ring-opening between the --O-- and the adjacent keto group to form various kinds of adducts. Thus, with an acid RCOOH, the caprolactone opens and reacts as follows: ##STR2## where n is an integer.
With an alcohol ROH, the caprolactone (n mols) splits in the same way to give: ##STR3##
It will be evident from the above that the reaction of the acid or alcohol with the caprolactone can be used to introduce terminal --COOH and/or --OH groups in the product.
The invention is based on the finding that by polymerizing together (1) a mixture of vinyl monomers, including at least one such monomer containing an --OH or --COOH group, and (2) an .epsilon.-caprolactone, the resulting polymer demonstrates certain particularly useful properties for coating purposes. For example, the resulting product reacts particularly well with conventional melamine-formaldehyde precondensates to give coatings or films which show outstanding exposure resistance and are particularly useful as metal coil coatings or the like. Accordingly, the principal object of the invention is to provide certain acrylic copolymers which are uniquely useful, particularly with amino-formaldehyde precondensates, for coating purposes. Other objects will also be hereinafter apparent.